This invention relates to split stator armature winding, and more particularly to armature windings arrangement for a split stator of a dynamoelectric machine in which the stator can be relatively easily assembled and disassembled.
In a.c. machines in which the armature windings are mounted on a stator, the stator must be circumferentially divided when the size of the machine exceeds a certain limit for shipping. Also, the stator must be circumferentially divided when there is not enough space for handling the rotor for axially inserting and withdrawing the rotor from the stator at the time of field installation, inspection, and servicing.
A conventional split armature winding is constructed as shown in FIG. 1, in which three-phase, single layer windings having hexagonal coils are disposed in two slots per pole per phase. The armature windings are wound in a single-layer for convenience of connection and separation at the location of the dividing line. In the figure, a stator iron core 1 is divided and is separable along the dividing line X--X. The stator iron core 1 has a plurality of slots (not known) in which armature coils 2a, 2b and 2c are inserted. The armature coils 2a illustrated by solid lines are of phase U, the armature coils 2b illustrated by dash lines are of phase V, and the armature coils 2c shown by dot-and-dash lines are of phase W. Each of the armature coils 2a, 2b, 2c has winding start lead 3a and an end lead 3b. The connections between the coils in the different phase are not illustrated. The coils 2a, 2b or 2c in the same phase are connected by a connection 4.
In a manufacturing shop, the split stator is put together to form a circular bore therein, and the armature coils 2a, 2b, 2c are inserted in the respective slots formed in the stator iron core 1 and the coils 2a, 2b, 2c are electrically connected. Then, a rotor is assembled in the stator, and the assembled machine is tested. After the test, the stator is divided at the dividing line X--X for shipping. In order to divide the stator shown in FIG. 1, the armature coils 2b having coil ends which extend across the dividing line X--X must be removed from the slots of the stator iron core 1. One of the sides of each coil 2a, 2b, 2c is always below one of the sides of the neighboring coil. For example, armature coil 2b has its right-hand side under the left-hand side of armature coil 2c. Therefore, in order to remove armature coil 2b on the division line X--X from the stator, the left-hand side of the adjacent armature coil 2c must be removed from the slot.
When the divided machine is assembled in the field, the armature coil 2b on the dividing line X--X must again be inserted into the stator slots together with the coil side of the adjacent coil 2c which was removed.
Thus, with the conventional armature winding as shown in FIG. 1, the armature coils must be inserted into the stator slots for testing, and the armature coils which extend across the dividing line of the stator core as well as the side of the adjacent coil must then be removed from the stator slots in order to disassemble the stator for shipping, and the armature coils must again be inserted into the stator core slots when assembling the machine in the field. Also, the coil conductors, which are heavily insulated, are firmly inserted within the slots by means of wedges, and the rotor must be pulled out from the stator before the coil inserting and removing operations can be performed. Therefore, the repeated forced insertions and removals of the coils from the slots in the stator iron core may damage the insulating layer of the coil conductor. Moreover, these operations are time-consuming.
In order to eliminate these above discussed disadvantages of the above-explained conventional arrangement, the use of separable armature coils as shown in FIG. 2 has been proposed. In FIG. 2, the general construction is the same as that shown in FIG. 1 except that the armature coils 2b having coil ends which extend across the dividing line X--X have brazed joints 6. During assembly, the joints 6 are brazed and coated with an insulating layer, and when disassembled the joint 6 can be heated by a torch to melt the brazed joint 6. Therefore, this arrangement eliminates the need for the repeated forced insertion and removal of the armature coils 2b and sides of the adjacent coil 2c. However, this arrangement entails a time-consuming and difficult brazing operation, and the coil conductors must be heated to an elevated temperature, so that the dividing operation still takes a long time and the insulation on the coil conductors can be easily damaged by heat during brazing.